226 PRACTICAL ORGANIC CHEMISTRY
hot water, then with- warm dilute caustic soda and water again.
Yield, 10 12 grams.
Sublimation. A portion of the dry substance may be
purified by sublimation. It is placed (23 grams) on a large
watch-glass, which is heated on the sand-bath over a very small
flame. The watch-glass is covered with a sheet of filter paper,
which is kept flat by a funnel placed above. After five minutes
or so pale yellow, needle-shaped crystals of anthraquinone will
have sublimed on to the filter paper.
C0H ' I \CflH4 + 2Cr03 + 6C,H4Oa = CflH4< >CrtH.,+
Properties. Yellow needles: m. p. 277 ; sublimes at 250 ;
b. p. 382" ; insoluble in water, soluble in acetic acid, less soluble
in benzene and other organic solvents.
Reaction. Add a little dilute caustic soda to a small quantity
of anthraquinone, and then a little zinc dust. On heating to
boiling, an intense red colouration is produced, which disappear^
on shaking. Sodium oxanthranolate, C<5H., .
formed, which oxidises in the air to anthraquinone.
Appendix, p. 316.
Anthraquinone /^monosulphonate of Sodium,
CGH 4/Ł°\C0H3.SOaNa + H,O
Graebe, Liebermann, Annalcn, 1871,160, 131 ; A. G. Perkm,
30 grms. anthraquinone.
30 fuming sulphuric acid (40 per cent. SO;.).1
The 40 per cent, fuming sulphuric acid is removed from tin;
bottle by cautiously melting it in a sand-bath, and it is then
weighed, out in a flask (Ł litre). The anthraquinone is added,
and the flask attached by a cork to an air-condenser. Tin.?
1 As fuming sulphuric acid is difficult to keep In an ordinary stoppered butt I**
without absorbing moisture, it is advisable to coat the stopper with a layer Ťyf
paraffin wax, and a substantial covering of plaster of Paris above this.